The customer brought this 2002 Chevrolet Silverado 2500HD, with a 6.6 liter diesel engine in, with the complaint that the batteries go dead and is slow cranking sometimes. He had replaced the batteries and the problem got better but is now starting to happen more often. The batteries on a dual battery system have to be checked a little different than a single battery system. The first thing that I did was to isolate the two batteries from each other and load tested them individually. To do this I only had to remove one ground cable and perform a load test at each battery. The driver’s side battery failed the load test and had to be replaced. Common thinking would be that this would be the cause of the customers complaint but I wanted to be absolutely sure. The next step was to check the starter draw from each battery. The new battery was was supplying 217 amps at 11.01 volts.
The older, passenger side battery was supplying 8 amps at 12.78 volts. This clearly showed me that there was a problem with the battery cables between this battery and the engine. I inspected the ground cable to make sure it was clean and tight at both the battery and the engine block. It was good.
The same could not be said for the positive cable.
I removed the terminal bolt and pulled the red cover off.
I then got my side post battery terminal brush. I found this design brush several years ago and I thinks it is the greatest thing in the world for cleaning side post battery terminals. To order one of these battery brushes please click here.
They attach to any 1/4 inch drive tool but I prefer a cordless 1/4″ power driver.
I put the brush to work and in just a minute or so both sides of the –
-terminal were clean. I finished cleaning the rest of the odd shaped parts of the terminal with a standard hand wire brush.
I then wrapped the cable with a rag and sprayed the terminal with an aerosol lubricant that leaves a protective barrier.
I finished by coating it with dielectric grease. Make SURE BOTH of the ground cables are safely away from the batteries while working with the positive cable. One wrong move and you will burn a hole in the a/c line.
Installed the red cover and a new bolt. To order new bolts please click here.
Now it is safe to connect the ground but first I did a drain test with both of the battery grounds disconnected. No drains present.
I retested the system and now both batteries supply and equal amount of amperage to the starter during cranking.